Apparatus and method of grading grinding wheels in rotation



Jan. 7, 1964 R. 0. LANE 3,116,632

APPARATUS AND METHOD OF GRADING GRINDING WHEELS IN ROTATION Filed Oct. 26, 1961 FIG. 2

2 Shets-Sheet 1 INVENTOR R/CHARD 0. LANE ATTORNEY Jan. 7, 1964 QNLANE 3,116,632

APPARATUS AND METHOD OF GRADING GRINDING WHEELS IN ROTATION Filed Oct. 26, 1961 2 Sheets-Sheet 2 FIG. 3

LOAD

DYNAMOMETER PREAMPLIFIER RECORDER FIG. 5

INVENTOR R/C'HARD 0. LANE flaw-Quad ATTORNEY United States Patent 3,116,632 APPARATUS AND METHOD OF GRADING GRINDING WHEELS IN ROTATION Richard 0. Lane, Munith, Mich., assignor to Macklin Company, Jackson, Mich., a corporation of Michigan Filed Oct. 26, 1961, Ser. No. 147,914 11 Claims. (Cl. 7378) The invention pertains to a method and apparatus for grading grinding wheels and pertains to a method of grading the hardness and other characteristics of a grinding wheel while the wheel is rotating.

Abrasive grinding wheels are manufactured by several basic processes and the grinding wheel art has become very specialized in that many types of wheels are available wherein the grinding characteristics, strength, smoothness of cut, size, etc. are important individual requirements for a wheel designed for a particular grinding application. Over the years of existence of the grinding wheel art, manufacturers have been able to produce grinding wheels with specialized characteristics for particular applications by varying the composition of the wheel, the composition of the abrasive bond, the type of bond, the shape of the wheel, the type of abrasive and other components as well as varying the method of manufacture. However, no satisfactory means has heretofore been devised for accurately determining the overall characteristics of a grinding wheel within specified limits, and it is the basic object of the invention to provide a method and apparatus for very accurately grading the characteristics of a grinding wheel wherein the quality control of grinding wheels may be vastly improved, and defects and variations in the characteristics of a single wheel may be readily determined.

The grinding characteristics of grinding wheels have for many years been considered to be related to the hardness of the wheels and many devices and methods for testing the hardness and rate of metal removal of grinding wheels have been devised. Such methods commonly employ the use of steel specimen of standard characteristics which are held in engagement with the wheel under predetermined pressure and time conditions wherein the amount of the specimen removed is determined. Also, common hardness testing devices include hardened or diamond-tipped penetrating points which are held in engagement with the wheel and rotated or oscillated a predetermined degree under known pressure conditions wherein the penetration of the tool is used as an indication of the grinding wheel hardness. Such hardness testing apparatus has been useful in obtaining a rough determination of the grinding wheel characteristics. However, the methods employing steel specimen make only a very rough determination of the grinding wheel characteristics. Testing devices penetrating the wheel material are not able to provide an accurate evaluation of the wheel characteristics over the complete cutting face in that only that portion of the wheel engaged by the penetrating point is tested, and it would be neccessary to take many readings on each wheel to completely evaluate the characteristics 'of a wheel. For practical reasons such extensive testing is untenable.

It is the intention and purpose of the invention to provide a method and apparatus for grading grinding wheels wherein the determination of the grinding wheel characteristics may be determined during the conventional facing and sizing operation of the grinding wheel and wherein the accuracy of the grinding wheel characteristics evaluation is such that grinding wheels of similar composition manufactured under identical conditions may be very closely, selectively, and qualitatively graded. It would be assumed that grinding wheels of similar composition manufactured under identical conditions, would be identical in ice characteristics; however, this is not the case due to the slight inconsistencies which may exist in the composition, operation of the forming machines, and mixing of the wheel ingredients prior to forming, and inconsistencies gnthe chemical reaction occurring during drying and ring.

The effective hardness of a grinding wheel, among other factors, will be influenced by the sharpness or dullness of the individual abrasive grains, the elastic properties of the bond supporting the individual grains, the elastic properties of the bonded abrasive grains considered as a body or structure, and the elastic properties of the entire system including the machine upon which the grinding wheel is mounted.

Also, the hardness of the grinding wheel will vary due to the ability of the individual grains to maintain a cutting edge and clean itself of the material cut from the material being removed. The aforementioned factors are very difficult to evaluate individually, and the only practical method of determining the relative hardness of grinding wheels is in testing the characteristics of the wheel as a whole. It will be appreciated that merely testing the wheel wear resistance of a grinding wheel or the ability of the grinding wheel to remove metal from a standard specimen, will not provide a complete analysis of the aforementioned factors affecting hardness.

In the practice of the invention, a conventional conical grinding wheel facing tool mounted upon a free-running spindle is passed across the periphery of the grinding wheel at a predetermined radial cut and feed speed. During this facing operation wherein the facing tool is removing the material of the grinding wheel primarily by a crushing action, the forces necessary to perform the cutting or crushing by the facing tool are accurately measured and recorded. In this manner the entire periphery of the grinding wheel is encountered and tested by the facing tool pressure sensing apparatus as it passes across the entire width of the wheel. Also, as the testing of the wheel is taking place while the wheel is being formed to its final size, the characteristics of the wheel as provided to the customer are determined and elfective grading and quality control may be achieved.

It is, therefore, an object of the invention to provide a method and apparatus for grading grinding wheels wherein the wheel may be graded upon a conventional grinding wheel facing machine during the final facing operations, and the characteristics of the grinding wheel may be very accurately determined during during the facing operation.

Another object of the invention is to provide a method and apparatus for grading and testing grinding wheels wherein the grinding wheel is tested completely throughout its periphery and across the complete width of the face thereof.

Yet another object of the invention is to provide a method and apparatus of testing grinding wheels wherein a permanent comparative record of each testing operation is maintained and recorded wherein comparison of wheels of similar composition and manufacturing processes is possible permitting a high degree of quality control in the grinding wheel art, and wherein a very accurate comparative grading system between similar wheels, and even dissimilar wheels, may be provided.

A further object of the invention is to provide a method and apparatus of testing grinding wheels which does not significantly add to the time of manufacture and final shaping of the grinding wheel and which produces a permanent record of the grinding wheel characteristics which may be very quickly interpreted.

These and other objects of the invention arising from the details and relationships of the steps and components of an embodiment of the invention will be apparent from the following description and accompanying drawings wherein:

FIG. 1 is a perspective view of a conventional grinding wheel facing machine showing the apparatus necessary for the practice of the invention mounted thereon,

FIG. 2 is a plan view of the relationship of the grinding wheel to the conventional and dynamometer mounted facing tools supported upon the facing machine table,

FIG. 3 is a plan sectional view of the dynamometer mounted facing tool in accord with the invention,

FIG. 4 is an elevational, enlarged, detail view of the strain gauge chamber of the dynamometer with the chamber cover removed, and

FIG. 5 is a block diagram of the load sensing and recording apparatus employed in the practice of the invention.

The relationship of the basic components necessary to practice the invention will best be appreciated from FIGS. 1 and 2 wherein a conventional grinding wheel facing machine is illustrated having a base and a shaft 12 rotatably mounted thereon and driven by a motor, not shown. A grinding wheel 14, to be faced, is mounted upon the shaft 12 and dust removing means 16 are normally located adjacent the facing area as shown. A carriage 18 is mounted upon the base 10 for movement in a direction parallel to the axis of the shaft 12. Carriage 1 8 is actuated by both manual and power means of a conventional type wherein the speed of the carriage travel may be very accurately controlled under power feed. A compound 20 mounted upon the carriage supports a conventional conical grinding wheel facing tool 22 rotatably mounted within the tool support 24. The compound 20 may be radially adjusted inwardly and outwardly with respect to the grinding wheel by means of a feed screw actuated by handle 26. All of the above described structure is found on conventional grinding wheel facing machines and comprises no part of the invention except as set forth below.

In the practice of the invention a second compound 28 is mounted upon the carriage 18 and is movably mounted in a radial direction with respect to the grinding wheel by a handle 30 affixed to a threaded shaft, not shown. The dynamometcr mounted conical grinding wheel facing tool 32 is mounted upon the compound 28 by means of the dynamometer mechanism 34 which is fixed to compound 28. The output of the dynamometer 34 is fed into a preamplifier 36 supplying a recording device 38 which is usually located adjacent the facing machine, and preferably in a dustproof housing, although it will be appreciated that the electronic apparatus may be located at any desired location.

In normal practice, facing of the grinding wheel periphery 40 is necessary to size the grinding wheel to the proper diameter and produce an accurate grinding surface. The facing tool 22 is located such that the axis thereof will preferably be on a angle with the axis of travel of the carriage, e.g. the axis of the grinding wheel. The compound 20 is located during facing such that the innermost point of the tool 22, as indicated by point 42, FIG. 2, will engage the wheel and remove that portion of the grinding wheel encountered by the tool as it moves across the peripheral face 40 of the wheel. The action of the facing tool is primarily a crushing action as the tool will very rapidly rotate due to the fact that it is driven by the rotating grinding Wheel. The initial passes across the width of the grinding wheel are termed preliminary or rough cut passes and are used to bring the diameter of the wheel near the desired final diameter. Upon each pass of the tool across the face of the grinding wheel, the handle 26 will be rotated to move the tool further into the wheel to the desired depth of the cut. As the final diameter of the grlnding wheel is approached, the depth of cut is reduced and upon reaching the proper wheel diameter the tool will be passed several times across the face of the grinding wheel to insure an accurate diametrical dimension. Thereupon, the grinding wheel is removed from the shaft 12 and another wheel placed thereon and the cycle repeated.

In accord with the invention, the axis of the dynamometer mounted facing tool 32 is also located at a 45 angle to'the axis of the grinding wheel and is at with respect to the axis of the facing tool 22. The facing tool 32 is also mounted for rotatable movement within the dynamometer and will rapidly rotate under the influence of the grinding wheel. The dynamometer 34 mounted upon the compound 28 will sense the axial forces imposed upon the shaft 44 mounting the facing tool 32, as well as the bending forces imposed upon the shaft in the horizontal direction radial to the grinding wheel. It has een found that the vertical bending forces imposed upon the shaft 44 tangential to the wheel are inconsequential and that the purposes of the invention may be accomplished by measuring and recording the axial and horizontal forces imposed upon the shaft 44 in that they are directly proportional to the force necessary to crush the grinding wheel material by the facing tool 32.

To practice the invention the operator will place the grinding wheel 14 to be faced and graded upon the shaft 12 and will afiix the same thereon. Thereupon, with the compound 28 backed off such that the facing tool 32 will not engage the grinding wheel 14, the compound 20 will be moved inwardly such that the tool 22 may be used to make a number of roughing cuts across the width of the periphery 40 of the grinding wheel to insure that the grinding wheel will be of a complete cylindrical configuration prior to being engaged by the dynamometer mounted tool 32 and is of an oversize which can be reduced to the desired size in the desired number of grading or sizing cuts. After the initial roughing cut or cuts are achieved by the tool 22, the compound 20 will be backed away from the grinding wheel and the compound 28 will be moved toward the grinding wheel wherein the facing tool 32 may now be used to make several final sizing and grading passes across the grinding wheel periphery.

After the roughing cuts by tool 22, the initial or preliminary pass of the tool 32 may be of a small depth to insure the cylindrical configuration of the wheel. Thereupon, the remaining finishing cuts or passes made across the periphery of the wheel 14 by the dynamometer mounted facing tool 32 will be of a uniform standard depth, and the crushing forces imposed upon the facing tool produce an axial and horizontal transverse force within the shaft 44 which will be sensed by the dynamometer 34 and recorded by the permanent recording device 38. After each pass of the facing tool 32, the compound 28 will be moved in the standard sizing and grading distance and passed across the width of the grinding wheel periphery 40. Each cut will be recorded and a sufficient number of cuts will be taken to properly size the grinding wheel. It will be appreciated that several passes across the grinding wheel will be used to determine the characteristics of each wheel, and by a comparison of the characteristics of each pass, the results of the passes may be compared for uniformity and averages tabulated.

To permit grading between different grinding wheels and to permit a standard to be determined, it will be appreciated that the rate of feed of the carriage during the dynamometer mounted facing tool cuts and the depth of the cut be standard as well as maintaining uniformity of the facing tools, etc. It has been found that accurate evaluation of the grinding wheel characteristics may be determined by using a radial cut of .001 to .005 inch. However, deeper cuts may be taken if desired. Thus, the depth of each recording cut must be predetermined and maintained throughout the grading and facing of each group of grinding wheels to be compared. A carriage travel rate of .050 inch per revolution of the grinding wheel has been found to be suitable. The aforedescribed depth of cuts and carriage feed are for purposes of illustration only and are not to be construed as limiting values.

As the grinding wheel characteristics such as hardness, flexibility, etc., will be proportional to the amount of force necessary to maintain the facing tool in engagement with the grinding wheel at a given depth of cut and rate of carriage travel, the above described method of grading grinding wheels has been found to be of high accuracy, and as the sensing and the recording of the forces imposed upon the facing tool 32 are highly accurate and responsive, the above described method for determining grinding wheel characteristics is of higher accuracy than heretofore known methods. Variations in thegrinding wheel characteristics throughout the periphery of the wheel will be disclosed during the recording of the forces imposed upon the facing tool, as well as any variations existing in the grinding wheel characteristics across the width or thickness of the wheel. The use of the method of grading in accord with the invention adds little, if any, time to the facing operation of the grinding wheel over conventional practice in that the recorded grading passes of the tool are part of the facing procedure.

By way of illustrating a type of sensing means which may be employed with the facing tool 32, a dynamometer 34 which may be used with the invention is shown in FIGS. 3 and 4 in detail. The dynamometer includes a block member 46 Which may be afi'ixed to the compound 28 by means of bolts 48. The block 46 is provided with a slot 50 extending vertically through the block intersecting the right end thereof but terminating short of the left end to produce bifurcated portions 52 and 54 in the block. It will be noted that the bolts 48 firmly affix the portion 52 to the compound. No bolting means are associated with the portion 54 with respect to the compound. The bifurcated construction of the block produced by the slot 50 permits the portion 54 to flex relative to the portion 52 as the slot may open and close a slight degree as to have an imaginary pivot point located between the inner end of the slot 50 and the left end of the block 46.

Preferably the slot 50 is filled with a fluid or other means for dampening vibrations existing between the portions 52 and 54.

The end of the block 46 adjacent the inner end of the slot 50 is provided with a chamber 56 of less height and width than the block. The chamber consists of a rectangular recess having upper and lower surfaces 58 and 60, respectively, defined therein. It will be noted that the inner end of the slot 50 intersects the chamber 56. The chamber 56 is provided with a cap 62 affixed in place by a screw 64, and sealing means are employed to prevent the entry of foreign matter into the chamber.

A hearing mounting block 66 is firmly affixed to the portion 54 of the block 46. The attachment between blocks 46 and 66 is accomplished by means of dowel pins 68 fitted within closely sized holes in the blocks and a bolt member 70 having a head 72 Within a recess 74 and cooperating with a threaded hole 76 within block 66. It will be noted that the hole 78 in the portion 54 intersects the slot 50 and is smaller than recess 74. A sleeve 80 is imposed between the head 72 of the bolt 70 and the portion 54 wherein upon tightening of the bolt the tension forces created within the bolt will be imposed between the block 66 and the block portion 54. It will be appreciated that the bearing mounting block 66 is affixed solely to the portion 54 of the block 46.

Block 66 is provided with a bore 80 extending therethrough, having enlarged diameters formed on the end for receiving roller bearings 84. The shaft 44 is rotatably mounted within the roller bearings and conventional bearing take up and sealing means are employed to insure a very accurate running fit between the shaft 44 and bearings 82 and to prevent the entry of foreign matter into the bearing structure. The conical grinding wheel facing tool 32 is afiixed to the outer end of the shaft 44 which extends from the housing 86 enclosing the dynamometer structure. The bolt 88 permits replacement grinding wheel facing tools to be readily affixed to the shaft.

Four strain gauges are afiixed to the block 46 within the chamber 56. Two upper strain gauges 90 are centrally located on the surface 58, FIG. 4, and the other two strain gauges 92 are located directly below the upper strain gauges on the surface 60'. The strain gauges are cemented to the surfaces 58 and 60 and are so located as to sense very small movement taking place within the material of the block 46 in the chamber surfaces upon the spacing between the portions 52 and 54 varying. Suitable wiring and terminal connections 94 are associated with the gauges and block to permit the variations in the strain gauge electrical conducting characteristics to be sensed and transmitted to the preamplifier 36 by means of conventional wiring.

Thus, during facing of the grinding wheel 14 by the tool 32, the forces imposed upon the shaft 44 will cause the portion 54 to flex relative to the portion 52, causing elongation or contraction of the strain .gauges and a reading on the recording device proportional to the amount of deflection of portion 54. The imaginary pivot point of the portions 52 and 54 is a vertical axis between the left and right gauges, FIG. 4, and thus, one of the gauges on each surface will be under tension when the other is under compression. In effect, the block 46 functions somewhat like a clothespin wherein the fingers thereof may be flexed and by the use of the preamplifier the current variations produced in the strain gauges during operation of the dynamometer may be magnified and by feeding the output of the preamplifier into the recorder, permanent recording of the comparison of the forces imposed upon the shaft 44 may be obtained.

It will be appreciated that the dynamometer disclosed in FIGS. 3 and 4 is only one type of device which may be used in the practice of the invention. Any type of force measuring apparatus capable of mounting the grinding wheel facing tool and sensing. the forces imposed upon the shaft supporting the tool may be used in the practice of the invention. Likewise, many types of amplifiers and recording devices are available 'which are acceptable for purposes of the invention. By Way of example, a Sanborn No. 151 recorder has been used in conjunction with a -No. -1100 Sanborn preamplifier in a commercial form of the invention.

In that the grading and testing of the grinding wheels occur during dynamic rotation of the wheel, more accurate results are obtained than in grinding wheel testing methods when the wheel is stationary. Also, in that the grading of the wheel is not dependent upon the use of specimens to determine the amount of metal removable within a given period under given conditions and as the test may be incorporated directly into a conventional second operation necessary in the manufacture of grinding wheels, a most efficient and practical system for determining grinding wheel characteristics is produced.

It is appreciated that various modifications to the inventive concept may be apparent to those skilled in the art, and it is intended that the invention be defined only by the following claims.

I claim:

1. The method of determining grinding wheel characteristics comprising the steps of rotating a grinding wheel about its normal axis of rotation, engaging and traversing the circumference of the wheel across its axial width and penetrating the wheel a predetermined radial distance by means of a grinding wheel abrasive engaging and sensing tool, sensing the force imposed on the tool and indicating the magnitude of such force.

2. The method of determining grinding wheel characteristics comprising the steps of rotating a grinding wheel about its normal axis of rotation upon a grinding wheel facing machine, facing the grinding wheel a predetermined radial distance by means of a facing tool, sensing the force imposed on the tool during the facing operation and indicating the magnitude of such force.

3. The method of determining grinding wheel characteristics comprising the steps of rotating a grinding wheel about its normal axis of rotation, removing a predetermined radial amount of the wheel periphery by crushing the wheel material, sensing the force necessary to perform the removal operation and indicating the magnitude of such force.

4. The method of determining grinding wheel characteristics comprising the steps of rotating the wheel about its normal axis of rotation at a conventional facing operation velocity, rough facing the periphery of the grinding wheel with a facing tool, finish facing the grinding wheel a predetermined radial degree with a facing tool, sensing the force imposed on the facing tool during said finish facing operation and indicating the magnitude of such force.

5. The method of determining grinding wheel characteristics comprising the steps of rotating a grinding wheel about its normal axis of rotation at a conventional facing operation velocity, rough facing the periphery of the grinding wheel with a facing tool, making a plurality of finish facing operations across the periphery of the grinding wheel of predetermined and uniform radial degree, sensing the force exerted on the facing tool during said finish facing operations and indicating the magnitude of such force.

6. Apparatus for simultaneously facing and determining the characteristics of a grinding wheel comprising, in combination, a grinding wheel facing machine having a rotating grinding wheel mounting shaft rotatably mounted thereon, a facing tool mounting compound mounted on said machine movable with respect to a grinding wheel mounted on the shaft, a grinding wheel facing tool mounted upon said compound, force sensing means operatively associated with said facing tool sensing the forces imposed on said tool during facing of the grinding wheel and indicator means operatively associated with said sensing means indicating the forces sensed by said sensing means.

7. Apparatus for facing and determining the characteristics of grinding wheels as in claim 6, wherein said facing tool includes a rotatably mounted conical grinding wheel engaging tool, tool support means rotatably mounting said tool, resilient compound mounted means supporting said tool support means, said force sensing means being operatively associated with said resilient compound mounted means sensing the deflection thereof during facing of the grinding wheel.

8. Apparatus for facing and determining the characteristics of a grinding Wheel as in claim 6, wherein said sensing means includes a dynamometer operatively associated with said facing tool and said indicator means is operatively associated with said dynamometer and includes means continuously recording the output of said dynamometer during a facing operation.

9. Apparatus for determining the characteristics of a grinding wheel comprising, in combination, a grinding wheel, means rotating said grinding wheel about its normal axis of rotation, a grinding wheel engaging and sensing tool mounted adjacent said Wheel adapted to be moved into engagement with said wheel, sensing means operatively associated with said tool sensing the forces imposed thereon upon said tool cutting a predetermined radial distance into said grinding wheel and indicator means operatively associated with said sensing means indicating the forces imposed on said tool during engagement of said tool and grinding wheel.

10. Apparatus for determining the characteristics of a grinding wheel comprising, in combination, a grinding wheel, means rotating said grinding wheel about its normal axis of rotation, a rotatable grinding wheel crushing tool mounted adjacent said wheel adapted to be moved into engagement with said wheel, sensing means operatively associated with said tool sensing the forces imposed thereon upon said tool removing a predetermined radial amount of the grinding wheel material from the periphery thereof and indicator means operatively associated with said sensing means indicating the forces imposed on said tool during engagement of said tool and grinding wheel.

11. Apparatus for determining the characteristics of a grinding wheel as in claim 10, wherein said sensing means comprises a dynamometer operatively supporting said wheel crushing tool and said indicator means includes a recorder continuously recording the forces imposed on said dynamometer during engagement of said grinding wheel and cutting tool.

References Cited in the file of this patent UNITED STATES PATENTS 2,001,794 Melton May 21, 1935 2,252,993 Stewart Aug. 19, 1941 2,360,639 Asimow et a1. Oct. 17, 1944 2,620,386 Alspaugh et a1. Dec. 2, 1952 

1. THE METHOD OF DETERMINING GRINDING WHEEL CHARACTERISTICS COMPRISING THE STEPS OF ROTATING A GRINDING WHEEL ABOUT ITS NORMAL AXIS OF ROTATION, ENGAGING AND TRAVERSING THE CIRCUMFERENCE OF THE WHEEL ACROSS ITS AXIAL WIDTH AND PENETRATING THE WHEEL A PREDETERMINED RADIAL DISTANCE BY MEANS OF A GRINDING WHEEL ABRASIVE ENGAGING AND SENSING TOOL, SENSING THE FORCE IMPOSED ON THE TOOL AND INDICATING THE MAGNITUDE OF SUCH FORCE. 